So to run retroarch I need rejuvenate correct? And if I read the guide correctly I can only use it when near a computer as I have to renew licenses everyday? What is the purpose of renewing licenses as it seems running retroarch for this might make it a pain than using psp emulators.

For running RetroArch you need rejuvenate, you're correct. And to be able to use it you need to renew the licenses daily... more or less. If you open rejuvenate and run a homebrew, that homebrew can keep running all the time you want as long as you don't close that homebrew. It can be hours, days, months... maybe. You don't need to be close to a computer once the hombrew has been loaded into memory, so you can put your vita in sleep mode go wathever you want and don't let it run out of battery in order to keep that homebrew running. The problem comes when you want to change your homebrew, and you have two options. One is to close rejuvenate, renew your licence and run another homebrew, or you can use Vitashell and load all your homebrews on the Vita Memory Card, and each time you want to close a homebrew you can return to vitashell instead to close rejuvenate so your only preocupation now will be keep your battery charged. Another wise recomendation is to use AndroidDefiler instead of Vitadefiler in order to run rejuvenate with an android phone instead of your computer, it is more comfy and convenient if you ask me, and VitaShell is the only homebrew you need in your phone. If your rejuvenate hombrew closes, you need to renew your licenses though.